1. Field of the Invention
The present disclosure generally relates to turbine engines. More particularly, the present disclosure relates to systems and methods with which seal clearance within the engine can be adjusted to increase the effectiveness of the seals.
2. Description of the Related Art
Many turbine engines comprise a bearing compartment that contains various static and moving parts. Oil is used within the bearing compartment to lubricate those parts and reduce wear.
Typically, bearing compartments are sealed with a pressurized bearing compartment seal that is intended to inhibit leakage of oil from the bearing compartment. In some cases, the bearing compartment seal is positioned between the bearing compartment and a buffer air cavity into which relatively high-pressure air is pumped. By pumping relatively high-pressure air into the buffer air cavity, the cavity becomes pressurized, thereby creating a positive pressure differential between the buffer air cavity and the bearing compartment. The positive pressure differential promotes air leakage into the bearing compartment and therefore prevents or reduces oil leakage from the bearing compartment.
The aforementioned positive pressure differential between the buffer air cavity and the bearing compartment is often maintained with secondary seals that seal off the buffer air cavity from the remainder of the engine. Such secondary seals limit the escape of the relatively high-pressure air from the buffer air cavity, thereby maintaining relatively high pressure within the buffer air cavity.
Unfortunately, it can be difficult to maintain a positive pressure differential at low engine power settings. That difficulty is magnified in cases in which tolerance accumulation (i.e., the aggregate effect of the tolerances of the various individual engine parts) increases the clearance of portions of the secondary seals and therefore decreases their effectiveness. In particular, the increased clearance results in greater leakage of air from the buffer air cavity and, therefore, reduced pressure within the buffer air cavity, which may enable oil to escape the bearing compartment.